1. Field of the Invention
The present invention relates to a surgical cutter.
2. Background Information
There are many surgical procedures that require the cutting and aspiration of tissue. For example, in a retina re-attachment procedure the surrounding vitreo tissue must be removed before the retina is repaired. The cutting device must be delicate enough to remove the tissue without further damaging the retina. Vitrectomies are frequently performed with guillotine surgical cutters.
FIG. 1 shows a guillotine surgical cutter which include an inner sleeve 1 that moves relative to an outer port 2 of an outer sleeve 3. The sleeves 1 and 3 are coupled to a handpiece 4 that is held by a surgeon. The inner sleeve 1 is coupled to a vacuum system which pulls tissue into the outer port 2 when the inner sleeve 1 moves away from the port 2. The inner sleeve 1 then moves in a reverse direction past the outer port 2 to sever the tissue in a guillotine fashion. The vacuum system draws the severed tissue away from the outer port 2 so that the process can be repeated.
The inner sleeve 3 is connected to a diaphragm 5 and a return spring 6 that are rigidly attached to the handpiece 4. The diaphragm 5 is adjacent to a pneumatic drive chamber 7 that is in fluid communication with a source of pressurized air (not shown) that is controlled by a solenoid air valve (not shown).
In operation, the inner sleeve 1 is in an open position so that tissue is pulled into the outer port 2. The solenoid air valve is then opened to pressurize the drive chamber 7 and expand the diaphragm 5. Expansion of the diaphragm 5 moves the inner sleeve 1 so that the tissue within the outer port 2 is severed by the sleeve 1. Expansion of the diaphragm 5 also deflects the spring 6. The air valve is eventually switched to vent the drive chamber 7. The spring 6 then pulls the inner sleeve 1 back to the original position so that the process can be repeated.
The drive chamber 7 has a relative large amount of fluidic capacitance which limits the speed of the device. Additionally, the spring 6 becomes stiffer as the diaphragm 5 expands and moves the inner sleeve 1. The relative high fluidic capacitance and spring stiffness increases the pressure requirements for the drive chamber 7. Having to pressurize the drive chamber 7 to a higher level reduces the speed of the cutter. Many prior art guillotine cutters have a cut rate in the range of 500 cuts per minute (CPM). At these speeds the guillotine cutter tends to pull the tissue. It would be desirable to provide a guillotine cutter that operates at higher speeds than cutters of the prior art.
There is only one aspiration port in the outer sleeve and a single opening in the inner sleeve which perform the guillotine cutting action. The inner sleeve typically moves within the outer sleeve to fully close the outer port. Closing the outer port creates an instantaneous change in pressure which causes the remaining tissue to bounce back and send shock waves throughout the vitreous body. It would be desirable to provide a guillotine cutter that would minimize the bounce back effect of severing tissue within the port of the cutter.